As techniques for efficiently utilizing a disc capacity of a storage apparatus, there are known a virtual volume technique and a deduplication technique (see PTL1, for example). The deduplication technique includes a technique of performing deduplication to all data stored in a storage subsystem, and a technique of performing deduplication to only specific pattern data registered in advance, and the latter is disclosed in PTL1. Further, in PTL1, there is disclosed a technique of suppressing a data volume of mapping information (virtual-physical mapping information) as management information utilized by the virtual volume technique and the deduplication technique.
In PTL1, the storage subsystem has a virtual volume, and a physical volume having a physical area allocated to the virtual volume. By dividing an address space of the virtual volume into a plurality of pages, the storage subsystem manages each of the plurality of pages by classifying the page into one state out of a plurality of states including at least a first state and a second state. Further, the storage subsystem manages a page classified into the second state, by further dividing the page into a plurality of segments. The first state is a state that, as a result of a write request received in a page, a physical area is allocated to the page, and data is stored in the physical area. The second state is a state that, as a result of a write request received in a segment in a page for writing write data that matches specific pattern data determined in advance, the specific pattern data and the segment are related to each other and managed.